HSA Distribution for non-dependent child on tax return under parent's medical insurance

You can claim medical expenses for a Qualifying Relative.

A qualifying relative is a person:

1. Who is your:
2. Son, daughter, stepchild, or foster child, or a descendant of any of them (for example, your grandchild),
3. Brother, sister, half brother, half sister, or a son or daughter of any of them,
4. Father, mother, or an ancestor or sibling of either of them (for example, your grandmother, grandfather, aunt, or uncle),
5. Stepbrother, stepsister, stepfather, stepmother, son-in-law, daughter-in-law, father-in-law, mother-in-law, brother-in-law, or sister-in-law, or
6. Any other person (other than your spouse) who lived with you all year as a member of your household if your relationship didn't violate local law,
7. Who wasn't a qualifying child (see Qualifying Child, earlier) of any taxpayer for 2024, and
8. For whom you provided over half of their support in 2024. But see Child of divorced or separated parents, earlier, Support claimed under a multiple support agreement next, and Kidnapped child under Qualifying Relative in Pub. 501.

See What Expenses Can You Include This Year?

Use the  IRS Worksheet for Determining Support. You may be able to claim your child and the expenses.

from PUB 969

nses.
Qualified medical expenses are those incurred by the following persons.
1. You and your spouse.
2. All dependents you claim on your tax return.
3. Any person you could have claimed as a dependent on your return except that:
b. The person had gross income of $5,050 or more;

 

Your son is too old to be claimed as a qualifying child dependent. Thus, to be claimable (you don't actually have to claim him)  as a dependent, the qualifying relative tests must be met. The relationship test is met. The gross income test is waived. The support test requires you to pay more than 50% of his support.

 

if you meet the support test, those are qualifying medical expenses for purposes of paying them out of the HSA. Each year, you must review the support test to see if you pay more than 50%,  

 

If you did/do not meet the requirements, any withdrawal to pay his medical expenses would be subject to regular income taxes and a 20% penalty.   

Thank you for the guidance. What does the support test include and how would I prove we paid more than 50% of his support?